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Summer Moon Illusion
Summer is a good time to spot giant moons very near the horizon. It's the season for the mysterious moon illusion.
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June 24, 2002
Sometimes you just can't believe your own eyes.
Tonight is one of those times. Go outside around 9:00 p.m. and look east. Rising above the horizon you might see a giant moon. Bright, very likely pink or orange, and swollen. The moon is real, but its surprising diameter is an illusion--the "moon illusion."
The moon illusion is a well-known trick of the eye: a low-hanging moon looks unusually big. The moon is really the same size (0.5 degrees wide) no matter where it appears in the sky--photographs prove it--but the human eye and brain tell us differently.
A time-lapse sequence of the moon rising over Seattle. To the camera, the moon appears to be the same size no matter what its location on the sky. [More]
Image credit: Shay Stephens.
Summer is a good time to experience the moon illusion because the full moon never gets very far above the horizon. (The Sun and the full moon are on opposite sides of the sky. So when the Sun rises high--as it does during summer--the full moon hangs low.) Tonight's full moon, the first of northern summer, will hug the horizon long after moonrise.
Low-hanging moons often glow pink or orange. That's no illusion. Dust, smoke and pollution scatter moonlight and make the moon itself look colorful for the same reason that sunsets often glow vivid shades of red. Smoke and ash from summertime wildfires in North America will add an extra dash of color to the moon this week.
(Full Story Here)
Cheers,
Dan
Summer Moon Illusion . . .